A conventional chain, for example, a roller chain for use in a power drive disclosed in an Unexamined Japanese Utility Model Publication No. SHO 56-71545, includes an inner link assembly having a pair of inner plates disposed in parallel with each other and a pair of hollow cylindrical bushes press-fitted in fore and aft portions of the inner plates, and an outer link assembly having a pair of outer plates disposed in parallel with each other and a pair of pins press-fitted in fore and aft portions of the outer plates. The inner link assembly and the outer link assembly are alternatively connected. In addition, provided around each bush is a roller which engages a sprocket.
In this type of chain, there is a sliding contact between the bush and the pin. Furthermore, there is a sliding contact between the bush and the roller. In order to facilitate such a sliding contact, lubricant oil is coated or supplied between the bush and the pin, as well as between the bush and the roller. When this lubricant oil leaks out during the operation of the chain, abrupt abrasion between the bush and pin, and between the bush and the roller will occur due to a lack of lubricant oil.
In the roller chain disclosed in the above-mentioned publication, an O-ring made of elastic materials is provided in a compressed state so as to touch the end face of the bush and located between the surfaces of the inner and outer plates which face one another. Furthermore, an O-ring made of elastic materials is provided in a compressed state between the outer surface of the bush and the inner surface or the edged of the roller. These O-rings prevent lubricant oil leakage from between the bush and the pin, and between the bush and the roller to the outside thereof.
In order to retain the lubricant oil, however, the O-rings are compressed between the inner and outer plates or between the bush and the roller. Therefore, if the compressive force upon the O-rings is large, the O-rings will be quickly worn down by the bending motion of the chain, which results in that the lubricant oil will no longer be retained, and therefore the abrasion between the bush and the pin, and between the bush and the roller will progress.
On the other hand, if the compressive force upon the O-rings is small, the lubricant oil retaining function decreases. Due to this, the lubricant oil between the bush and the pin, and between the bush and the roller easily leaks out, causing inferior lubrication.
Furthermore, if the compressive force upon the O-ring is large, the resistance to the bending motion of the chain and the rotational resistance of the roller will become large, thereby the transmission loss of the driving power will become large when the chain is in operation.
Therefore, the clearance between the surfaces of the inner and outer plates which face one another, as well as the clearance between the outer surface of the bush and the inner surface of the roller must be strictly managed, and an appropriate compressive force must be given to the O-rings. In order to accomplish this, not only would the measurement accuracy of each part have to be improved, but the assembly accuracy of each part would also have to be improved.
The object of the present invention is to provide a chain that can prevent lubricant oil leakage between the bush and the pin, and between the bush and the roller, and that can retain the lubricant oil therebetween.
Another object of the present invention is to provide a chain that, in allowing excellent bending motion of the chain, can retain the lubricant oil between the bush and the pin, and between the bush and the roller.
Another object of the present invention is to provide a chain that, in allowing easy manufacturing of each part which makes up the chain and easy assembly of these parts, can retain lubricant oil between the bush and the pin, and between the bush and the roller.
Still another object of the present invention is to provide a chain that can supply lubricant oil between the bush and the pin, and between the bush and the roller.